Electrical contact



March 24, 1931. F. KUHN ET AL 1,797,581

ELECTRICAL CONTACT Filed Oct. 18, 1926 awue'wtoza [76 2? 17/212 Zarraza'e /Z. 72mm;

. M W mom,

Patented Mar. 24, 1931 UNITED- STATES PATENT I OFFICE FRANK KUHN AND LAURENCE H. THOMAS, OF DETROIT, MICHIGAN, ASSIGNOES TO.

AMERICAN ELECTRICAL HEATER COMPANY, OF DETROIT, MICHIGAN, A CORPORA- TION OF MICHIGAN ELECTRICAL CONTACT Application filed October 18, 1926. Serial No. 142,412.

The invention relates to electrical contacts more particularly designed for use in connection with electrical heaters and it is the primary object of our invention to insure l suificient contact pressure to maintain a good electrical connection. In the present state of the art contact devices of this type are usually formed of resilient metal which is initially under sufficient tension to firmly hold the contact surfaces in engagement. However the pressure between the contacting surfaces is insuificient to hold them in good connection which results in sparking and eventually in destroying the contacts.

To overcome this defect we have devised a construction where the heating eiiect instead of reducing contact pressure will intensify it. This is preferably accomplished by the use of a composite metal bar the constituents thereof having different coeflicients of expansion and being-so arranged that when heated a warping of the bar is produced. Various specific constructions may be used embodying the essential features of our invention but the drawings illustrate specifically a socket contact embodying our invention and in which Figure l is a plan view of the socket contact.

Figure 2 is a central longitudinal section on line 22 of Figure 1.

Figure 3 is a cross section on line 3-3 of Figure 1, showing the cooperating contact in engagement with the socket.

Figure 4 is a perspective view of the thermostatic element.

' A and B are complementary segmental contact members for embracing a thin contact member C. The member A may be formed with an ear D having a threaded aperture for receiving the clamping screw E for securingthe electrical conductor. This member A is also shown as provided with parallel side flanges F, flat portions G adjacent thereto and a segment H central of said flat portions. The member B is similar in form with omission of the flanges F and adapted to fit between said flanges on the member A. This also is provided with a hooked portion I which engages an aperture J in the member A.

K is a composite metallic bar which is bent into a U-form and extends through the aperture J to embrace the members A and B. This member K is formed of constituent metals having difierent coeflicients of expansion and so arranged that a rise in temperature will cause the legs of the U to bend to-' ward each other. Thus, whenever the parts of the contact become heated the member K will be placed under additional tension and will press the members A and B against the member (J more firmly than when all the parts are cold. This will insure the greatest pressure when the device is in use and will eventually-prevent sparking between the contacting surfaces.

What we claim as our invention is:

1. An electrical contact device comprising a split socket contact and a single member embracing the sections of said contact mem-" ber on opposite sides of the split adapted to increase the pressure thereon upon rise in temperature.

2. An electrical contact device comprising a split contact member and a U-shaped member embracing the portions of said contact upon the opposite sides of the split, said'U-,

shaped member being formed of a composite bar the constituent elements of which have different coefiicients of expansion and which are arranged to increase the pressure on said contact member upon rise in temperature.

3. An electrical contact device comprising a segmental sobket'contact member, a complementary segmental socket contact member, and a U-shaped member embracing said contact members, said U-shaped member being formed of a composite metal bar the constituent elements of which have different coefficients of expansion and which is adapted when heated to increase the pressure upon said contacts. I

4. An electrical contact device comprising an expansible socket contact, and a single resilient member for resisting expansion of 'tially U-shaped resilient member for resistsaid contact, the tension of said member being increased upon a rise in temperature.

5. In an electrical contact device, the combination with cooperating contact members, of a single resilient member for pressing said contact members toward each other and adapted to increase the pressure thereon upon a rise in temperature.

6. An electrical contact device comprising a segmental socket device having an extension provided with an opening, a complefnent'ary segmental socket contact member having a projection received in said opening,

and resilient means for pressing said contact members toward each other and adapted to increase the pressure thereon upon a rise in temperature.

7 An electrical contact device comprising a segmental socket contact member having spaced, laterally extending flanges and an extension provided with an opening, a complementary segmental socket contact member positioned between said flanges and having a projection extending through said opening, and a U-shaped resilient member pressing said contact members toward each other and adapted to increase the pressure thereon upon a rise in temperature.

8. An electrical contact device comprising an expansible socket contact and a substaning expansion of said contact, the tension of saidmember being increased upon a rise 1n.

temperature.

In testimony whereof we afix our signatures.

FRANK KUHN. LAURENCE H. THOMAS. 

